Air springs of the type referred to above are known per se and are used in very diverse applications. German patent publication 42 30 249 C2 discloses such an air spring with a metal cover which is connected securely in an air-tight manner to the flexible member by a flanging process. In order to avoid damage to the components with full compression of the air spring, a rubber stop buffer oriented towards the interior of the air spring is arranged on the cover. This stop buffer is fastened to a corresponding lug welded to the cover. The abutment face between the stop buffer and the cover is flat.
In U.S. patent application publication 2004/0222577, an annular stop buffer is provided which is arranged in a spring pot of metal.
The solutions disclosed have metal air-spring covers in order to transmit the occurring buffer forces to the adjacent ancillary components without damage to the cover.
For reasons of weight-saving, plastics are also increasingly used for the ancillary components (pistons and covers) which seal the air spring flexible member.
U.S. patent application publication 2005/0236749 shows a two-part air spring cover wherein the rolling-lobe flexible member is clamped between an outer cover and an inner cover of plastic with the latter being latched in the outer cover. Here too, however, the stop buffer is mounted on the metal outer cover.
If the covers are formed completely of plastic, a ribbing is preferably provided for stiffening for reasons of strength.
However, the use of a buffer in combination with the ribbed structure of the cover is problematic because, with the buffer mounted either on the piston or on the ribbed side of the cover, the buffer is destroyed by the inwardly-oriented ribs of the cover with repeated impact of the components on the buffer.
An arrangement of the ribbing of the cover on the outside of the cover is usually avoided because foreign bodies or water can collect in the cavities formed by the ribs which, in extreme cases, for example frost, can lead to the destruction of the cover. As a result, the air spring cover is usually made of metal, or is made from plastic only when an internal stop buffer is not provided.